1. Field of the Invention
This invention relates to devices for harvesting a patient's own blood lost during surgery, defoaming and filtering the blood, and readministering it to the patient intravenously.
2. Description of Prior Art
Because of the danger to a patient's health resulting from the loss of any quantity of blood, either the result of injuries or during surgery, it has become common practice to maintain the patient's blood volume by the transfusion of homologous banked blood. However, there are several well known complications resulting from the administration of homologous blood. In some instances, the homologous banked blood has carried serum hepatitis. In other instances, patients have had acute reactions to transfusion or have had blood types that were difficult to cross match because of complexities in the blood chemistry. In order to reduce or eliminate the demand for homologous banked blood, attempts have been made over the years to collect the patient's own blood lost during surgery and return it to him. In early attempts, surgeons collected the blood from the abdomen by a ladle or cupped hands and placed it in basins or flasks containing sodium citrate. This blood was then returned to the patient intravenously. Later developments included the collection of blood by a suction line and filtering the blood through gauze and then readministering it to the patient. These attempts were cumbersome and subject to contamination.
Early attempts to provide a closed means for withdrawing the blood utilized glass or pyrex vessels for receiving the blood. It was a simple matter to apply vacuum to such vessels which were provided with suitable inlet hoses and probes for extracting the blood for the surgical field. However, it was found that the hard surfaces of the receiving vessels caused considerable damage to the blood components, and it was evident that less damage would occur to the blood if a soft plastic bag, such as that used in blood transfusion work, could be used. However, early attempts to apply vacuum to a blood collection bag failed, because atmospheric pressure caused the bag to collapse under the action of the vacuum. One of the objects of the present invention is to eliminate the need for the hard glass receiving vessels and allow the use of the softer plastic receiving vessels.
In recent years, a closed circuit autotransfusion device has been developed consisting of a roller pump for withdrawing the blood from a surgical field and transferring it to a rigid sterile reservoir at an elevated location. The blood collected in the reservoir is then returned to the patient via direct pressure produced by the roller pump. Filtering is accomplished in the reservoir and in the return lines.
However, this device has a distinct disadvantage in that once the reservoir has been filled or partially filled with blood, a layer of blood remains on the inside of the reservoir thereby falsely giving the appearance that a considerable quantity of blood is in the reservoir when actually the reservoir may be nearly empty. This creates a dangerous situation since the operator may continue to reinfuse blood from the reservoir to the patient. As the blood is being reinfused under direct pressure from the action of the roller pump, if the blood supply in the reservoir is exhausted, air from the reservoir will be forced into the patient causing an air embolism with fatal results. There have been several cases where this has happened. Despite this danger and the cost of such equipment, it is currently available commercially and is in use in many hospitals.
A second device that has had limited use utilizes a standard plastic blood collection bag located inside a vacuum chamber. When a vacuum is applied to the chamber in the area between the chamber and the blood bag, the bag is caused to expand, thereby exerting a vacuum or suction on the inlet line leading from the bag to the patient. Although this device eliminates the use of a roller pump, it is necessary to stop the device when the bag is full, open the vacuum chamber, remove the full bag of blood, connect a new collapsed, plastic blood bag to the suction line, and transfer the full bag to an elevated stand whereby the blood was reinfused through the action of gravity into the patient.
Although this second apparatus has the advantage of eliminating the roller pump, it cannot be operated continuously, as it requires certain down time for removing the full bag of blood and placing an empty bag in its place, reclosing the vacuum chamber, and again applying vacuum to the area between the bag and the chamber to cause the bag to expand and create a vacuum on the inlet line to the bag. In addition, this device is not capable of use in those situations where any appreciable volume of air will be drawn into the bag. This device would not be usable in the normal surgical situation where the volume of air to blood drawn into the bag would be 10 to 1 or more, because unless the bag is substantially full of blood, the anticoagulant material that is in the bag prior to its use will be in excess of the normally desired amount. Moreover, if unwanted air is drawn into the bag, it will require frequent changing of the bags to accommodate any volume of blood. Consequently, because of its inability to accommodate any appreciable volume of air, this device is limited to use in cases of hemothorax.